1. Field of the Invention
The present invention relates to a method for managing document data and a data structure including document data.
2. Description of the Related Art
An Information Technology (IT) environment has recently been developed. The IT environment development causes, for example, the increase in CPU processing power, in capacity of storage devices such as a RAM, a hard disk drive and a removable disk, in communication speed, in scan resolution of scanners, and in display resolution of displays.
In relation to that, large volumes of electronic documents can be easily replicated (copied) and distributed to many places.
In this way, document distribution becomes convenient. At the same time, however, it can be said that the leakage of confidential information and privacy information is liable to occur. Efforts are required to prevent such information leakage.
For example, a method is often used of managing document data in a server in a centralized manner and of requesting password entry upon distributing data. In addition, a method is often used of distributing data after being encrypted. According to these methods, only a person who has a password or a decryption key can browse documents.
There is proposed a method described in Japanese unexamined patent publication No. 2002-183141. According to this method, in response to a request for permission to browse a document from a browsing terminal, a document managing server issues browsing permission and a unique code. The browsing terminal receives the browsing permission to browse the document and puts the unique code in the document to update the document.
It is unclear how distributed data is dealt with after distribution. Stated differently, it can be said that data becomes in an unmanaged state after distribution. In view of network development in recent years, data traceability is very important in order to enhance the certainty of information management. Accordingly, it is conceivably possible to use a method described in Japanese patent publication No. 3383793.
According to the method, a contents copying machine reads a contents ID from a contents copy original in which a contents ID is embedded and transmits the contents ID and information of a copy event attribute that are read to a contents ID management center via network. The contents ID management center acquires the original of the contents from the received contents ID, gives a new contents ID to the original, records the information of the contents ID and the copy event attribute, embeds the new contents ID to the original of the contents and returns the result to a copy request source. The contents copying machine outputs the returned original as a copy result.
Japanese unexamined patent publication No. 2003-99303 discloses an invention relating to a data structure. Japanese unexamined patent publication No. 2004-102627 discloses a method for determining a correlation between the original document and a replicated document.
New document data is being generated on a daily basis. Besides, as described above, large quantities of generated data can be easily replicated and distributed. Thus, a large sever is required to trace where data is present and to manage data in a server in a centralized manner, which incurs a high cost.